Electronics Worksheet: Components and Ohm’s Law Test

Electronics lesson 20: Part 2 test: components and Ohm’s law · Set 789 · 40 questions

Remember (Find the topic, use the formula): Find the topic and the formula: V = I × R, I = V ÷ R, R = V ÷ I, P = V × I, units = W × h ÷ 1000. Change mA to A and kΩ to Ω before using a formula. Check: put your answer back into the formula.

1. 1.🌈 A resistor has the colour bands violet, grey, black. What is its value (in ohms)?
2. 2.📏 How many milliamperes (mA) is 2.45 A?
3. 3.True or false: on an LED, the shorter leg is the anode (+). (a) False (b) True
4. 4.🔺 A current of 25 mA flows when 5.5 V is joined across a resistor. What is its resistance (in ohms)?
5. 5.Which of these saves electricity? (a) leave the TV on standby (b) leave fridge door open (c) use LED lamps (d) run fans in empty rooms
6. 6.What does a fuse do? (a) blows if current is high (b) senses how bright it is (c) is a resistance knob (d) makes a beeping sound
7. 7.🔺 The voltage stays the same and the resistance gets bigger. The current … (a) gets smaller (b) gets bigger (c) stays the same (d) becomes zero
8. 8.🧩 Which component smooths a wobbly supply? (a) capacitor (b) resistor (c) fuse (d) potentiometer
9. 9.⚡ A 2.25 W device works on 1.5 V. What current does it take (in amperes)? =
10. 10.🧮 A 0.4 V battery is joined to 2 Ω and 2 Ω resistors in series. What current flows (in amperes)? =
11. 11.📏 How many milliamperes (mA) is 0.53 A?
12. 12.🔺 A current of 25 mA flows through a 120 Ω resistor. What is the voltage across it (in volts)? =
13. 13.🌈 A resistor has the colour bands grey, yellow, red. What is its value (in ohms)?
14. 14.⚡ A home appliance on the 230 V mains takes 1 A. What is its power (in watts)?
15. 15.🔺 A current of 0.25 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
16. 16.🔍 Which is the odd one out? (a) iron one shirt at a time (b) switch off empty rooms (c) unplug idle chargers (d) close the fridge quickly
17. 17.True or false: to unplug idle chargers wastes electricity. (a) True (b) False
18. 18.🔺 A current of 20 mA flows through a 220 Ω resistor. What is the voltage across it (in volts)? =
19. 19.🔺 A current of 40 mA flows through a 100 Ω resistor. What is the voltage across it (in volts)? =
20. 20.🔺 A current of 10 mA flows through a 470 Ω resistor. What is the voltage across it (in volts)? =
21. 21.🧮 A 0.7 V battery is joined to 4 Ω and 3 Ω resistors in series. What current flows (in amperes)? =
22. 22.💡 Why does an LED need a resistor in series? (a) to make it brighter (b) to limit the current (c) to store charge (d) to change its colour
23. 23.🌈 Which colour bands (1st digit, 2nd digit, multiplier) mark an 830 Ω resistor? (a) orange-grey-brown (b) grey-orange-red (c) grey-orange-black (d) grey-orange-brown
24. 24.🧮 Two resistors in parallel give a total that is … (a) more than either one (b) their sum (c) less than either one (d) always zero
25. 25.🧮 Four equal 100 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
26. 26.📏 Which unit measures current? (a) ohm (Ω) (b) volt (V) (c) watt (W) (d) ampere (A)
27. 27.🧮 Three equal 15 Ω resistors are joined in parallel. What is the total resistance (in ohms)?
28. 28.🔺 A 1.2 V supply is joined across a 120 Ω resistor. What current flows (in milliamperes, mA)?
29. 29.🔺 A current of 2 A flows through a 5 Ω resistor. What is the voltage across it (in volts)? =
30. 30.Which of these is measured in watts (W)? (a) current (b) voltage (c) resistance (d) power
31. 31.📏 Which unit measures the push of a cell? (a) volt (V) (b) watt (W) (c) ampere (A) (d) ohm (Ω)
32. 32.True or false: energy used each second is measured in amperes (A). (a) False (b) True
33. 33.🧩 Which part changes electrical energy into sound? (a) a capacitor (b) a resistor (c) a buzzer (d) a diode
34. 34.⚡ A device works on 5 V and takes 2 A. What is its power (in watts)? =
35. 35.Which of these is measured in amperes (A)? (a) power (b) voltage (c) resistance (d) current
36. 36.🔺 A current of 0.2 A flows through a 4 Ω resistor. What is the voltage across it (in volts)? =
37. 37.⚡ A 6 W device works on 3 V. What current does it take (in amperes)? =
38. 38.🧾 A 100 W appliance runs for 4 hours. How many units (kWh) of electricity does it use? =
39. 39.📏 Which unit measures how much a part resists? (a) volt (V) (b) watt (W) (c) ohm (Ω) (d) ampere (A)
40. 40.🌈 A resistor has the colour bands red, green, orange. What is its value (in ohms)?

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